Means for utilizing solid-state materials and devices for the electronic control of guided electromagnetic wave energy



Mar

Filed May 25. 1954 ch 8, 1960 M. A. LAMPERT 2,928,056 MEANS FOR UTILIZING SOLID-STATE MATERIALS AND DEVICES FOR THE ELECTRONIC CONTROL OF GUIDED ELECTROMAGNETIC WAVE ENERGY 2 Sheets-Sheet 1 Pip/#770 500205- I March 8, 1960 IM. A. LAMPERT 2,928,056 MEANS FOR UT LIZING SOLID-STATE MATERIALS AND DEVICES FOR THE ELECTRONIC CONTROL 0F GUIDED ELECTROMAGNETIC WAVE ENERGY 2 Sheets-Sheet 2 Filed May 25, 1954 IN V EN TOR. Wz/emyfl Mama/er Murray A. Lanapert, Brooklyn, N.Y., assignor to Radio Corporation of America, a corporation of Delaware ApplicationMay 25, 1954, Serial No. 432,165

8 Claims. (Cl. 332-54) This invention relates generally to the control of guided electromagnetic wave energy and particularly re lates to means for achieving such control by varying the density of charge-carriers in semiconducting materials and devices interposed in the 'path of the wave energy and external to the source of the electromagnetic energy.

An electromagnetic wave travelling in a selected. mode along a transmission line is characterized by its phase and ainplitude. In some instances such as where there is more degeneracy (as'in circular waveguides) polarization also is important. However, the problem of propagation control is mainly a problem of phase and amplitude control.

At present thereare a number of wave propagation control devices, usually gas-tubes, in which the controlling element is" an electron gas which is created and maintained in a gaseous discharge. The term electron gas is well known and is defined as a cloudof electrons wherein the electrons move with random velocities (in both direction and magnitude), except for the drift velocity which the cloud as a whole may possess. The electron cloud thus constitutes' a medium for energy propagation and, as such, may be used to determine the phase and amplitude of an electromagnetic wave propagated therethrough.

The parameters of the electron gas which govern the kind (i.e., phase shift or attenuation) and degree (magnitude) of propagation control are the electron density,

the electron-molecule. collision frequency, and the effects of external magnetic or electric fields to which the electron gas is subjected.

Since the density of the electron gas in the discharge some cases, for example, transmit-receive (TR) and asaas s Patented Mar. 8, 1960 ice for solid-statematerials and devices for .controlling the propagation of guided electromagnetic wave er Another object of the invention is to control the propagation of guided electromagnetic wave energy controlling the density of charge-carriers in solid-state materials and devices.

A further object of the invention is to provide 1213* proved means for controllingguided wave propagation in other than gaseous atmospheres.

A still further object of the invention is to utilize solidstate materialsrand devices for electronically controlling guided wave propagation in apparatus in which gas tubes or the like are mechanically inconvenient or cannot be used.

A still further object of the invention is to control ided wave propagation by controlling the chargecarrier density of a semiconducting body.

Electronic propagation control with solid-state semiconducting devicesmay be achieved in several diiferent ways: (1) through variation of the charge-carrier density, (2 through variation of the collision frequency of charge-carriers which is a rather diiticult method of control from a practical standpoint), and (3) through changes in the charge-carrier orbits in the solid by virtue of magnetic or electric fields impressed thereon. The present invention primarily is concerned with the first mechanism, namely, variation of the charge-carrier density. The charge-carrier density may be varied as de-' sired by iradiating the solid with one'or a combination of neutral particles (light quanta, neutrons, gamma rays,

etc), charged particles (alpha particles, beta rays, thermally produced electrons, protons, ions, etc.) and by voltage? or current control applied to the semi-co nfductorv material.

Applications for solid-state wave propagation control devices are numerous. Particularly important applications for such control are amplitude modulation, phasernodulation, frequency-modulation, and electronic switch- I The invention will be described in greater detail with reference to the accompanying drawings in which:

Figure-1 is a perspective view of a first embodiment of the invention in which the propagation of microwave energy is controlled by utilizing a modulated beam of light or a nuclear emission source to control the'density of charge-carriers in a semiconducting body;

Eigure'Z is a perspective view of a second embodiment I of the invention 'in which the propagation of microwave antitransmit-receive (ATR) tubes, the radio-frequency power incident on the gas either partially or completely controls the electron gas density.

in accordance with the present invention, it has been found that improved wave propagation control and other features of the invention, mentioned below, are attain- A me-' diumfor the control of the phase and amplitude of able by means other than a gaseous discharge.

guided waves has been found to exist in solid-state semi: conducting materials.

carriers in the semiconducting material. These chargecarriers are the aggregates of electrons in the conduction proved means for electronically controlling the propaga'-' tion ofguided electromagnetic wave energy.

'Another object-oftheiiivention is t'oprovide means" This medium includes chargeenergy is controlled byvoltage control of the density of charge-carriers at a p-n junction in a semiconducting body;

Figure 3 is a perspective view of a third embodiment of the invention in which the propagation of wave energy in a broad-band ridge waveguide is controlled in accordance with the invention;

Figure 4 is a schematic diagram of a fourth embodimerit of the invention wherein microwave energy propagated along a surface waveguideis controlled according to the invention.

Similar reference characters are applied to similar elements throughout the drawings.

Referring to Figure 1, microwave energy from a source, not shown, is propagated through a hollow waveguide 10. -A pair of inductive conductive diaphragm or iris elements 16 and 17 extend inwardly from the H- planeor narrow walls of the waveguide 10 and a pair of hollow conductive capacitive posts 11 and 12 extend into the waveguide from its E-plane or broad walls.

The diaphragms 16 and 17 and the posts 11 and 12 preferably are located in a common plane transverse to the lon'gitudinahaxis of the guide and comprise a resonant escapee tially pure semiconducting rnaterial, i.e., a material 7 wherein relatively few donor or acceptor atoms are present. Typical materials which may be utilized in the present apparatus include germanium, silicon, and other semiconducting materials such as cadmium sulfide, the latter being one of the intermetallic compounds. For purposes of the present example a germanium body is selected, the intrinsic region preferably having aresistivityof at least 30 ohm-centimeters. The resultant nintrinsic-p device 13 preferably may comprise either a grown junction device or an alloy junction device. In the latter case the n-type conductivity region may be formed, for example, by alloying a pellet 3 of a material such as arsenic, antimony, or alloys including these materials into one surface of the semiconducting body. The p-type region is formed, for example, by alloying a pellet Ssuch as indium, gallium, boron, or alloys including these materials into an opposed surface of the body. For a detailed description of the alloying technique per se, reference may be made to a copending application Serial No. 294,741, filed June 20, 1952, by Charles W. Mueller, now Pat. No. 2,894,862, issued July 14, 1959. Although the semiconducting device 13 shown preferably is an nintrinsic-p device, it will be appreciated that a p-n junction device or other type of semiconducting device may be employed.

The H-plane or narrow walls of the waveguide each preferably include apertures 18 and 19 through which radiation from one or more radiation sources 8 and 9 outside the waveguide 10 may be directed to impinge upon the intrinsic region 7 of device 13. The apertures 18 and 19 preferably are longitudinally offset with respect to each other and are located on opposite sides of the plane in which the diaphragms 16 and 17 are located. The use of at least two oppositely disposed radiation sources permits substantially the entire surface area of the intrinsic region 7 of the semiconductive device 13 to be irradiated.

When the radiation from the sources 8 and 9 is inci dent upon the semiconducting device 13, the chargecarrier density within the intrinsic material is increased or varied in accordance with the intensity of the incident radiation. Changing the density of charge-carriers (electrons and holes) within the intrinsic region changes the conductivity of the device 13. This change in conductivity results in a detuning of the resonant section including the inductive diaphragms 16 and 17 and the capacitive posts 11 and 12 and thereby results in a modulation of the amplitude and phase of the electromagnetic wave energy propagated within the waveguide 10. Thus, by controlling the intensity of the radiation, the electromagnetic wave energy may be amplitudeand phasemodulated to the extent desired. In the event that electron-hole recombination occurs at a slower rate than the rate of formation of holes and electrons, it may be desirable to apply a voltage to the n and p regions to sweep these charge-carriers out of the intrinsic region and effectively increase the speed of recombination. Such voltage may be applied when the rate of change of modulation exceeds the recombination capabilities of the semiconductor material.

In the event that the structure heretofore described is to be utilized for affording switching action rather than .4 attenuation or phase-shift of the propagated microwave energy, the intensity of the incident radiation need only be increased to the point where the density of the chargecarriers is sufficiently great to completely detune the resonant section of waveguide 10.

The radiation sources 8 and 9 may comprise either light ray emission sources or sources providing nuclear or charged particle emission. In the event that it is desirable to use nuclear emissions for controlling the semiconductor charge-carrier density, one or a combination of radioactive emitters such as strontium (a beta particle emitter), cobalt 60 (a gamma ray emitter), or polonium and uranium (alpha particle emitters) may be employed. Control or modulation of the charge-carrier density when utilizing radioactive emission sources may be provided by interposing a variable density absorbing plate (not shown) between the sources 8 and 9 and the waveguide structure. Also, a thermionic emission source, such as a cathode ray gun, not shown, may be utilized to produce a modulated electron beam for bombarding the semiconducting body. In this case, however, the region between the emission source and 'the semiconducting device 13 must be evacuated, and suitable electron generating and accelerating voltages must be provided. In the second embodiment of the invention shown in Figure 2, a modulation source 20 is connected to the n and p regions of the semiconducting device 13 via leads 21 and 22. The leads 21 and 22 are brought into the waveguide 10 through apertures 25 and 26 located in the E-plane Walls, the apertures being substantially aligned with the axis of the cylindrical hollow capacitive posts 11 and 12.

Control of the charge-carrier density is achieved in accordance with this feature of the invention by controlling the voltage applied across the semiconducting device 13. For the condition of zero modulation of the amplitude and phase of energy travelling through the waveguide 10, the modulation source 20 is adjusted to apply a strong reverse bias to the n and p regions of the device 13. This results in a condition of low conductivity inthe semiconducting device 13, or substantial depletion of charge-carriers in the intrinsic region. Modulation of microwave energy is accomplished by decreasing the reverse voltage toward zero. If a greater range of modulation is desired, the applied voltage may be increased in the forward direction (i.e., the polarity of the applied voltage is reversed). Changing the applied voltage in this manner increases the density of electrons and holes in the intrinsic region and increases the conductivity of the device 13. Since the device 13 is located in the waveguide 10 at a point of high electric field intensity, the amplitude and phase of microwave energy propagated therethrough are modulated in accordance with the instantaneous value of applied voltage. Thus the attenuation and phase shift of energy propagated in the waveguide 10 variees in accordance with variations in polarity and amplitude of the modulating voltage applied to the semiconducting device 13.

In the embodiment shown in Figure 3, a ridge waveguide 49 is employed for broad-band propagation of electromagnetic wave energy. The waveguide 49 includes ridges 31 and 32 projecting inwardly from the broad walls 35, 37, each of which includes an aperture or slot 25, 26. A semiconductive device 13 of any of the types heretofore described extends along at least a portion of the guide length and is positioned in the waveguide 49 and insulated from the edges of the aperturcd ridges 31 and 32 by insulating members 14 and 15. The device 13 preferably is positioned so that only the intrinsic region '7 of the device 13 extends between the ridges and is in the path of microwave energy travelling through the guide. A modulation source 20 is coupled to the n and p regions of the semiconductingdevice. The amplitude and polarity of the bias applied to the device may be controlled as described previously to modulate the phase and amplitude of the microwave energy.

A further embodiment of the invention shownin Figure 4 utilizes a dielectric rod or filament 41 as a surface waveguide along which electromagnetic energy is propagated. The rod 41 includes two members 45 and 47, each of which has a tapered end42 and 43 making ohmic or non-rectifying contact with opposed surfaces of the intrinsic region 7 of a semiconducting device 13. The device 13 preferably is of the n-intrinsic-p type described previously. .A source of modulating voltage is coupled to the n and p regions of the semiconducting device 13 by leads 21 and 22.

The filamentary type of surface waveguide and control mechanism described is particularly desirable for controlling electromagnetic energy in the portion of the fre-' quency spectrum between them'icrowave and infra-red wavelength bands. .The ends 42 and 43 of the dielectric rod 41 are tapered to provide the proper impedance match-between the dielectric rod 41 and the semiconducting device 13. The theory of operation of the propaga- 7 tion control mechanism for the instant structure is substantially the same as described with referenceto the structure shown in Figures 2 and 3. x

In summarizing, the present invention provides an efiective and relatively simple means for controlling guided electromagnetic energy by controlling the density of charge-carriers in"a semiconducting device. The semiconducting device is suitably situated in or coupled to the .path of the electromagnetic waves, and the charge-carrierdensity is varied in accordance with desired modulationby any one of several methods. These methods in- 9 clude irradiation of a semiconducting body with neutral or charged particles, or lightrays, or by varying the space charge at a p-n junction by varying the voltage across the junction. Variation ofthe charge-carrier density varies the phase and amplitude of energy propagated in the waveguide. The invention thusmay be utilized to advantage for amplitude-modulation, phase-modulation, frequency-modulation, or electronic switching of microwaves. a V

What is claimed is: 1

1. Electronic wave propagation control apparatus comprising, a rectangular hollowpipe'waveguide section having broad and narrow walls, an .inductive diaphragm extending transversely into said waveguide from each of said narrow walls, a pair of coaxially aligned capactive posts extending from said broadwalls into said waveguide adjacent the space withinsaid diaphragm, asemiconducting body supported between'said posts and insulatedtherefrom, and means for controlling the electricalconprising, a hollowpipe waveguide having cooperating ridges therein for propagating microwave energy, a semiconducting body'having a region of intrinsic conductivity and a p-type conductivity region and an n-type conduc tivity region, said device being supported between ridges of said ridge waveguide and insulated therefrom with said intrinsic region positioned in the path of said microwave energy, and a potential source connected to said p-type and n-type conductivity regions.

5. Electronic wave propagation control apparatus cornprising, a surface waveguide including a pair of spaced coaxially aligned rods, a semiconducting device having a region of intrinsic conductivity and a p-type conductivity region and 'an n-type conductivity region, said device being positioned between 'said spaced rods so that said rods make ohmic contact to opposed surfaces of said intrinsic region, and a potential source connected to said p-type and n-type conductivity regions.

6. Electronic wave propagation control apparatus as claimed in claim 1 and wherein said controlling means includes an arrangement ;for changing the charge-carrier density in said body.

7. Electronic wave propagation control apparatus com said broad walls into said waveguide adjacent thespace Within said diaphragm, a semiconducting body supported between said postsv and insulated therefrom, and means for irradiating "c said body to control thecharge-carrier density within said body to attenuate and thereby modutures being longitudinally oifsetwith respect to each other ductivity of said body to modulate microwave energy tial source connected to said p-type and n-type conductivity regions.

3. Apparatus as claimed in claim 2 wherein only said intrinsic region is disposed in the path ofsaid microwave energy.

4. Electronic wave propagation control apparatus comand located on opposite sides of the plane in which said diaphragm is' located, a first radiation source arranged to irradiate said body through one of said apertures, and a second radiation source aranged to irradiate said body through the other one of said apertures.

References Cited in the file of this patent UNITED STATES PATENTS 2,402,663 Ohl Iune25, 1946 2,514,678 Southworth July 11, 1950 2,556,881 McArther June 12, 1951 2,557,180 Fiske June 19, 1951 2,570,938 Goodrich Oct. 9, 1951 2,643,297 Goldstein June 23, 1953 2,740,940 Becker Apr. 3, 1956 2,743,322 Pierce Apr. 24, 1956 2,777,906 Shockley Jan. 15, 1957 2,790,088 Shive Apr. 23, 1957 2,815,487 Kaufman Dec. 3, 1957 2,856,589 Kazan Oct. 14, 1958 John Wiley and'Sons (New York), 1953. Page 28 relied upon. 

